Separation of mono-and di-alkyl esters of sulphuric acid



July 31, 1945- H. F. KOHLER SEPARATION OF MONO-AND DI-ALKYL ESTERS OF SULPHURIC ACID' Filed Jan. 28, 194s ...tu r3.5

ATTR/VEY @alienated July 3l, i945 zssossz SEPABATIGN F MON- mil-Amm ESTEBS 0F SULPHUBIC ACID neuw F. nouer, Baytown, Tex.. Standard Oil Development Gompany, a

ration oi' Delaware Application January 28. 1943, Serial No. @78.190

The present invention is directed to the separation of thernoncand di-alkyl esters of sulphuric acid.

t is well mown to the art that sulphuric acid will combine with olens to form both the monoand ill-alkyl esters. There is evidence to indicate that a chemical equilibrium is set up which may be represented as follows:

* The equilibrium of the reaction may be altered by changing the concentration of the reactants. For examples low acid-olen ratio l(around 1:2) will give larger amounts of thedi-alkyl 'ester whereas a higher ratio (around 2:1) will give more ofthe mono-alkyl esters. While the equilibrium may be altered by regulating the conditions of the reaction, a mixture of the monoand di-alkyl esters is still obtained. There is a substantial commercial demand for the alkyl esters mentioned above, for example, in the alkylation ofisoparaiiins, andit is often desirable to separate the mono-alkyl ester from the di-alkyi ester.

The present invention is directed to the separation or fractionation of a mixture of monoan'd di-alkyl esters. The invention may be broadly describedas including the steps o1' obtaining a solution of both the monoand di-alkyl esters in a low boiling 'saturatedhydrocarbon and altering the concentration of the esters in thevsolution to selectively separate a mono-alkylester fraction and a dialkyl ester fraction.

A preferred manner of practicing4 the present y invention will now be described in conjunction with the drawing in which the single ligure is in the form oi `a diagrammatical iiow sheet.

Turning now specically to the drawing, suly phuric acid owing through pipe Il and a mixture of oieiins and low boiling saturated hydrocarbons owing through pipe t2 are conducted to a mixing vessel it where they are reacted in the well known manner to produce a mixture of monoand. di-allwl esters, Theitemperature within vessel i3 maybe regulated by .use ci a cooling coil I 4. The product from mixer I3 may be withdrawn to settling vessel I8 where it is separated under the innuence oi sravityto form an upper layer comprising esters dissolved inthe low boiling saturated hydrocarbon and acid hav-g ing dissolved therein smalleramounts Aof the esters. The acid fraction may be withdrawn from ester fraction, the solution of the monoand dil alkyl esters inv saturatedhydrocarbon is passed via line il to vaporizei E8 where a portion ot the saturated hydrocarbon is removed as vapor through line it. The product from the'vaporiaer may be withdrawn as bottoms and sent to settler 2t where the mono-alkyl esters are separated out as a heavy fraction under the inuence ol' gravity and are removed through drawofi line 2l. The lighter traction from settler at, comprising the saturated hydrocarbon with eli-alkyl esters dissolved therein as well as the residual monoallryl esters, may be passed to a second vaporizer ita where additional saturated hydrocarbon is removed therefrom through line -22 and then withdrawn via line 23 to settler 2t. ln this ves sel a di-alkyl ester fraction separates from the light hydrocarbon and may bewithdrawn iromthe bottom of the vessel via line 25.

It is generally desirable to regulate quite closelythe temperature at which the two fractions are separated in settling vessels 20 and 2l. respectively. and, accordingly. a heat exchanger 28 may' be arranged in the line between vaporizer I8 and settler 20 and heat exchanger 2l may be placed in the line between vapcrizer ld and settler fill. It is preferable to maintain vessels and 2t at dierent temperatures. For example, it has been found that good results may be obtamed by maintaining a temperature oi 20 F. in vessel 2@ and a temperature of 10 F. in vessel 2d. @n 'some occasions. a temperature of 10 ll". may be desirable in vessel t@ and `a. temperature ci 0 F. in vessel 2Q. temperatures may be maintained in the settling vessel as desired. l

The lighter fraction obtained by settling in vesn -sel tl comprises low boiling saturated hydrocar-n bons having dissolved therein the fumi.. of

mono-alkyl and ril-alkyl esters which were not' separated out in the vessels 2@ and Bt.- This ad mixture may be withdrawn from the system via line 28 if desired or may be recirculated by line 2t and admixed ,with the solution being withdrawn from vessel l5 to the rst vaporizer le. Alternatively, this solution may be passed via line It into vaporizer Il and a mixture or mixed esters withdrawn by line 32 and the-saturated hydrocarbon removed as vapors via line 33. f

the settler via line I6 and the hydrocarbon frac-7 tion vialine Il.

It will be understood that the acid withdrawn from the rst settling vessel i5 contains appreciable amounts of esters dissolved therein. This' solution of esters in the acid may be withdrawn from the system via line or i1' desired may' be extracted -with a suitable solvent to remove the It will also be evident that other traction tower 3i and allowed to iiow downwardly therein countercurrent to a suitable solvent. lit

- is desirable to use a low boiling saturatedhydro earbonasthesolventsotbattbeesters .maybe separated'in the remainder of tbesystem above described. Following this procedure, a light hydrocarbon is forced into the extraction tower 3B through line 38 and allowed to iiow up wardly in the tower countercurreutly to the sul.-l phuric acid. The sulphuric acid is withdrawn from the bottom of the tower via line 31 while the solution or esters in light hydrocarbon may be conducted from the'top of the tower via line 38 into line II and admixed with the light hydrocarbon and esters flowing from vessel 'I5 to vaporiner- Il. l

It vwill be apparent that the above described procedure is generally applicable to the sparation of monoand di-alkyl esters. A number of saturated hydrocarbons or saturated hydrocarbnn mixtures may be employed in eiiecting the separation oi the mono-alkyl from the di-alkyl esters, Normal butane has been found particu-y larly suitable for use .in this process. but other assesses ing asolution oi mono-alkyl sulphates and di# simi sulphates in a low boiling hydrocarbon soi- Yent, removing a portion oi said solvent Krom said solution by vaporization and settling to oba mono-alkyl' sulphate traction, removing said mono-amlsulphate fraction, vaporizing low boiling hydrocarbon solvent from the reminder and settling to obtain a cli-alkyl sulphate iraction and removing said cli-alkyl sulphate irac- 2. A method o! obtaining monoand di-alkyl esters comprising the steps of g sulphuric acid with olefin and low boiling saturated hydrocarbon and allowing said mixture to react to form monoand di-alkyl esters, passing the reaction product to a settling zone and allowing it to settle into a spent sulphuric acid fraction and a solutionoi monoand di-alkyl esters in hydrocarbon solvent. separating said fractions. vaporizing a portion of solvent from said solution to precipitate out a liquid mono-alkyl fraction.

settling to separate said mono-alkyl fraction from hydrocarbons such as propane, pentane. hexane andmixtures'oithesehydrocarbonsarealsosatisiactory. In commercial' operations, esters formed by the reaction of sulphuric acid with butylenes are particularly in demand but the procedure above described may obviously be applied A to other alkyl-esters formed by`. the reaction of sulphuric acid with olefins such as amylencs and hmlenes. Having fully described and illustrated the-presentinventimwhatldesiretoclaimisp l. A method o! separating a'mixture of momo anddi-alkylesterscomprlsingtbestopsofform- 40 the remaining solution, vaporizing additional hydrocarbons from said solution to precipitate a liquid di-alkyl ester fraction and settling to remove said fraction.

3. A method in accordance .with claim 2 in which the sulphuric acid withdrawn from said -nrst settling zone is extracted with low boiling saturated hydrocarbon solvent and said extract is passed through said vaporizing and settling zones to separate a mono-alkyl ester and a dialkylester fractiontherefrom.

A. A method inaccordance with claim 2 in which the low boiling hydrocarbon solvent withdrawn from said second settling zone is passed to a subsequent vaporizing zone and the -hydrocarbon is vaporlaed from residual esters.

HENRY is. nomina 

